The digital revolution has intruded in almost every sphere of modern electronic communications and has given rise to applications and abilities that were not even considered prior to the introduction of the small platform computer system in the late 1960's and its subsequent development through the 70's, 80's and 90's. Although totally pervasive in every aspect of society and sector of the economy, the digital revolution has had a significant impact in the field of electronic communication and, most particularly, to that area relating to the capture, transmission and faithful reproduction of audiographic and videographic data. No one field has benefited more from the capabilities generated by the digital revolution than that of telemedicine.
Functionally, telemedicine allows a physician to have a remote site capability by means of which they are able to direct procedures, make diagnosis, and generally engage in the practice of certain forms of medicine without the need to be physically present in the operating theater or the examination room in order to effect a practically real-time interaction. In the field of pathology, specifically, telemedicine (telepathology to be more precise) allows the investigating pathologist to be separated from the local origin of tissue to be investigated and, ideally, still be able to make an effective investigation of a tissue sample in order to render a diagnostic opinion.
The current trend in telemedicine in general, and telepathology in particular, gives rise to some very interesting implications for the quality of healthcare services available to the public at large. Telepathology particularly allows a surgeon about to perform an invasive surgical procedure, to select a particular specialist without regard to that specialist's location. Selection of pathology services need only be made, therefore, by determining those most suited, or experienced, in dealing with the particular organ system under consideration. In the daily routine of a large hospital, such service flexibility becomes highly relevant when the diverse character of the procedures carried out as such hospitals is considered. Likewise, small to medium sized hospitals, which may not be able to support a large pathology staff incorporating the many subspecialties required for full coverage, are able to avail themselves of the same quality of pathology services that one might find in a major urban hospital. Clearly, the benefits of telemedicine, particularly telepathology, would be most greatly felt by small to medium sized hospitals in remote areas of the country where the size and quality of specialty medical staff is necessarily limited to due to geographical isolation.
The enabling tool for providing telepathology services is a telemicroscopy system connected to a bi-directional telecommunications network which is pervasive enough to allow the necessary equipment to be set up and operated virtually anywhere. Conventional forms of telemicroscopy equipment are generally well known in the art and suitably comprise a remote controlled microscope system where microscope images are acquired with a conventional video camera and transmitted, for display, to a control system. Remote operation of the microscope system and remote display of transmitted images can be realistically performed using a variety of communications technologies. However, in order to ensure a general availability of a developing telepathology network, interconnectivity is most realistic in the context of narrow band or broadband landline connections. Narrow band systems (like PSTN and ISDN) generally guarantee worldwide availability for very low costs, but at the price of bandwidth and/or channel capacity. Broadband systems (like ATM) allow enhanced channel capacity but still suffer from a lack of sufficient bandwidth to allow video transmissions at anything approximating real-time. Because of these limitations, conventional telemicroscopy systems have had to make certain compromises between channel capacity and image quality. The higher the quality of the transmitted image, the longer the time it takes to complete a transmission. Conversely, when transmission speed is an overriding concern, image quality necessarily suffers.
With a limited bandwidth available on PSTN (Public Switched Telephone Network) and ISDN (Integrated Services Digital Network), the only means available to increase transmission speed is to reduce the average number of transmitted bits per image, i.e., compress the digital image data developed by video camera. Before telepathology services become truly viable, image transmission must operate at bit rates of only a few hundred kilobits or a few megabits per second, which can only be achieved through rather large compression of the data.
Most sensory signals contain a substantial amount of redundant or superfluous information. For example, a conventional video camera, that captures approximately 30 frames per second from a stationary image, produces very similar frames, one after the other. Compression techniques attempt to remove the superfluous information from repetitive frames, such that a single frame can be represented by a reduced amount of finite data, or in the case of time varying images, by a lower data rate. It is well known in the art that digitized video signals comprise a significant amount of statistical redundancy, i.e., samples are similar to each other such that one sample can be predicted fairly accurately from another. By removing the predictable or similarity component from a stream of samples, the video data rate can be reduced. Such statistical redundancy is able to be removed without perturbing the remaining information. That is, the original uncompressed data is able to be recovered almost exactly by various inverse operations. The algorithms used in a compression system depend on the available bandwidth, the features required by the application, and the affordability of the hardware required for implementation of the compression algorithm on both the encoding and decoding side.